Display panel and driving method thereof

ABSTRACT

Provided are a display panel (10) and the driving method thereof. The display panel (10) may include a first substrate (110) and a second substrate (120) opposite the first substrate (110). The first substrate (110) may include a pixel unit (100), and the pixel unit (100) may include a light emitting element (101) and a first transistor (112) for driving the light emitting element (101) to emit light. The second substrate (120) may include a second transistor (122). The second transistor (122) may be configured to have a second drift value of a second threshold voltage which has a specific relationship with a first drift value of a first threshold voltage of the first transistor (112) under same ambient condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of the filing date of Chinese PatentApplication No. 201811004718.2 filed on Aug. 30, 2018, the disclosure ofwhich is hereby incorporated in its entirety by reference.

TECHNICAL FIELD

The embodiment of the disclosure relates to display technology, inparticular, to a display panel and a driving method thereof.

BACKGROUND

In a field of display technology, an organic light-emitting diode (OLED)display panel has advantageous characteristics such asself-luminescence, high contrast, low energy consumption, wide viewingangle, fast response, flexible panel, wide temperature range, simplemanufacturing, etc. The OLED display panel has broad prospects fordevelopment. In an OLED display panel, a thin film transistor whichconnects with OLED and drives the OLED is usually called a drivingtransistor. Stability of a threshold voltage of the driving transistorhas an important effect on the display quality of the OLED displaypanel.

BRIEF SUMMARY

An example of the present disclosure provides a display panel. Thedisplay panel may include a first substrate and a second substrateopposite the first substrate. The first substrate may include a pixelunit, and the pixel unit may include a light emitting element and afirst transistor for driving the light emitting element to emit light.The second substrate may include a second transistor. The secondtransistor may be configured to have a second drift value of a secondthreshold voltage which has a specific relationship with a first driftvalue of a first threshold voltage of the first transistor under sameambient condition.

Optionally, the first drift value of the first threshold voltage of thefirst transistor caused by a temperature is substantially the same asthe second drift value of the second threshold voltage of the secondtransistor caused by the temperature.

Optionally, the second transistor is substantially identical instructure and material as the first transistor, and the specificrelationship is that the second drift value is proportional to the firstdrift value.

Optionally, active layers of the first transistor and the secondtransistor have the same size and are made of the same material, and thespecific relationship is that the second drift value is the same as thefirst drift value.

Optionally, doped regions of the active layers of the first transistorand the second transistor have the same size and doping concentration.

Optionally, channel regions of the active layers of the first transistorand the second transistor have the same aspect ratio.

Optionally, an orthographic projection of the second transistor on thefirst substrate substantially overlaps an orthographic projection of thefirst transistor on the first substrate.

Optionally, the pixel unit comprises a plurality of pixel units, theplurality of pixel units comprising a plurality of first transistors.The second substrate comprises a plurality of second transistors, andthe plurality of second transistors is in one-to-one correspondence withthe plurality of first transistors.

Optionally, the pixel unit comprises a plurality of pixel units, theplurality of pixel units comprising a plurality of first transistors.The second substrate comprises a plurality of second transistors, andeach of the plurality of second transistors corresponds to two or moreof the plurality of first transistors.

Optionally, the second substrate further comprises a detection circuitcoupled to the second transistor, and the detection circuit isconfigured to detect the second threshold voltage of the secondtransistor.

Optionally, the detecting circuit comprises a third transistor, a fourthtransistor, and a first capacitor. A gate and a first terminal of thethird transistor are configured to respectively receive a first scansignal and a data signal, and a second terminal of the third transistoris coupled to a gate of the second transistor; a first terminal and asecond terminal of the second transistor are respectively coupled to afirst power voltage and a first terminal of the fourth transistor; agate and a second terminal of the fourth transistor are respectivelyconfigured to receive a second scan signal and a detection signalrespectively; and the first capacitor is coupled between the gate andthe second terminal of the second transistor.

Optionally, the second substrate may further include a light shieldinglayer, and the light shielding layer is configured to shield the secondtransistor from external ambient light.

Optionally, the first substrate and the second substrate respectivelycomprise a first color filter layer and a second color filter layer; thefirst color filter layer is in an area between first black matrixcovering the first transistor; and the second color filter layer is inan area between second black matrix covering the second transistor.

Optionally, an orthogonal projection of the first color filter layer andthat of the second color filter layer on a first base substraterespectively substantially overlap with an orthographic projection ofthe light-emitting element on the first base substrate.

Optionally, the display panel is an organic light emitting diode displaypanel.

Another example of the present disclosure is a method of driving thedisplay panel. The method of driving the display panel may includecompensating for the first threshold voltage of the first transistor bydetecting the second threshold voltage of the second transistor.

Optionally, the driving method further includes establishing a specificrelationship between a threshold voltage compensation value of thesecond transistor and a threshold voltage compensation value of thefirst transistor.

Optionally, compensating for the threshold voltage of the firsttransistor by detecting the threshold voltage of the second transistorcomprises compensating for the threshold voltage of the first transistorby using the specific relationship and the detected threshold voltage ofthe second transistor.

Optionally, the threshold voltage compensation value of the secondtransistor is substantially equal to the threshold voltage compensationvalue of the first transistor.

Optionally, the driving method further includes obtaining a real-timetemperature by detecting the threshold voltage of the second transistor.Compensating for the threshold voltage of the first transistor bydetecting the threshold voltage of the second transistor comprisescompensating for the threshold voltage of the first transistor based onthe real-time temperature.

Optionally, obtaining the real-time temperature by detecting thethreshold voltage of the second transistor comprises obtaining atemperature-threshold voltage relationship curve of the secondtransistor, acquiring the real-time temperature by detecting thethreshold voltage of the second transistor and consulting with thetemperature-threshold voltage relationship curve of the secondtransistor.

Optionally, compensating for the threshold voltage of the firsttransistor based on the real-time temperature comprises obtaining atemperature-threshold voltage relationship curve of the firsttransistor, and acquiring the threshold voltage compensation value ofthe first transistor by using the real-time temperature and consultingwith the temperature-threshold voltage relationship curve of the firsttransistor.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical scheme of embodimentsof the present invention, a brief introduction will be given below tothe drawings to be used in the description of embodiments or relatedtechnologies. Obviously, the drawings described below relate only tosome embodiments of the present disclosure and are not limitations tothe present invention.

FIGS. 1A-1B are schematic diagrams of two 2T1C pixel circuits in relatedart;

FIG. 2 is a block diagram of a display panel according to one embodimentof the present disclosure;

FIG. 3 is a schematic cross-sectional view of a display panel accordingto one embodiment of the present disclosure;

FIG. 4 is a schematic diagram of a detection circuit provided accordingto one embodiment of the present disclosure;

FIG. 5 shows an example of a temperature-threshold voltagecharacteristic curve of a second transistor according to one embodimentof the present disclosure;

FIG. 6A shows a schematic structure of a second substrate according toone embodiment of the present disclosure;

FIG. 6B shows a schematic structure of a first substrate according toone embodiment of the present disclosure;

FIG. 6C shows a schematic structure of a display panel according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure will be described in further detail withreference to the accompanying drawings and embodiments in order toprovide a better understanding by those skilled in the art of thetechnical solutions of the present disclosure. Throughout thedescription of the disclosure, reference is made to FIGS. 1-6C. Whenreferring to the figures, like structures and elements shown throughoutare indicated with like reference numerals.

It should be noted that the features shown in the figure do not have tobe drawn proportionally. The present disclosure omits the description ofknown materials, components and process technology, so as not to obscurethe exemplary embodiments of the present disclosure. The examples givenare only intended to facilitate understanding of the implementation ofthe exemplary embodiments of the present disclosure and further enablethose skilled in the art to implement the exemplary embodiments.Consequently, these examples should not be construed as limiting thescope of embodiments of the present invention.

Unless otherwise specifically defined, the technical or scientific termsused in the present disclosure shall be of general significance to thosewith general skills in the field to which the disclosure belongs. Thewords “first,” “second,” and similar expressions used in the presentdisclosure do not indicate any order, quantity or importance, but areused to distinguish different components. In addition, in variousembodiments of the invention, the same or similar reference labelsrepresent the same or similar components.

A pixel circuit of an OLED display apparatus in the related art usuallyincludes several pixel units arranged in an array. Each pixel unitcontains an organic light-emitting element, namely an OLED component anda driving transistor. The pixel circuit is configured to drive the OLEDto emit light of predetermined intensity based on data signals. Thepixel circuit usually includes a 2T1C pixel circuit, which uses two TFTsand one storage capacitor Cs to realize basic function of driving theOLED to emit light. One TFT may be a switching transistor, which mainlyplays a switching function and controls transmission of the datasignals. The other TFT may be a driving transistor, which mainly plays adriving function and provides driving current for the pixel electrodessuch as cathode or anode of the OLED apparatus.

As shown in FIG. 1A, the 2T1C pixel circuit may include a switchingtransistor T1, a driving transistor T2, and a storage capacitor Cs. Inone embodiment, the switching transistor T1 and the driving transistorT2 are both N-type TFTs. A gate of the switching transistor T1 iscoupled to a gate line (scanning line) to receive a scan signal (Vscan),a first terminal of the switching transistor T1 is coupled to a gate ofthe driving transistor T2, and a second terminal of the switchingtransistor T1 is coupled to a data line to receive a data signal(Vdata). A first terminal of the driving transistor T2 is coupled to apositive terminal of the OLED, and a second terminal of the drivingtransistor T2 is coupled to a first power terminal (Vdd, high voltageterminal). One electrode of the storage capacitor Cs is coupled to thefirst terminal of the switching transistor T1 and the gate of thedriving transistor T2, the other electrode of the storage capacitor Csis coupled to the second terminal of the driving transistor T2 and thefirst power terminal. The cathode of the OLED is coupled to the secondpower terminal (Vss, low voltage terminal), for example, to ground. Thedriving method of the 2T1C pixel circuit is to control the brightnessand darkness (grayscale) of the pixel via the two TFTs and the storagecapacitor Cs. When a scan signal Vscan is applied through the gate lineto turn on the switching transistor T1, the data driving circuit uses adata voltage (Vdata) fed through the data line through the switchingtransistor T1 to charge the storage capacitor Cs, thereby storing thedata voltage in the storage capacitor Cs. The stored data voltagecontrols the degree of conduction of the driving transistor T2, therebycontrolling magnitude of the current flowing through the drivingtransistor T2 to drive the OLED to emit light. That is, the currentdetermines the gray level of the pixel illumination.

As shown in FIG. 1B, another 2T1C pixel circuit includes a switchingtransistor T1, a driving transistor T2, and a storage capacitor Cs, butthe connection manner thereof is slightly changed. More specifically,the difference of the pixel circuit of FIG. 1B with respect to FIG. 1Aincludes: the positive terminal of the OLED is coupled to the firstpower terminal (Vdd, high voltage terminal) and the negative terminal ofthe OLED is coupled to the second terminal of the driving transistor T2.Furthermore, the first terminal of the driving transistor T2 is coupledto the second power supply terminal (Vss, low voltage terminal), such asground. One electrode of the storage capacitor Cs is coupled to thefirst terminal of the switching transistor T1 and the gate of thedriving transistor T2, and the other electrode of the storage capacitorCs is coupled to the source of the driving transistor T2 and the secondpower supply terminal. The operational mode of the 2T1C pixel circuit isbasically the same as that of the pixel circuit shown in FIG. 1A, andthe details thereof are not described herein again.

In the OLED display panel, the driving transistors in the respectivepixel units may have different threshold voltages due to the differencein real-time temperatures. For example, a thin film transistor using anoxide semiconductor material as a channel material is liable to causefluctuations in the threshold voltage due to temperature change. Forexample, the pixel units at different positions may have differentreal-time temperatures due to different lighting time and lightingintensity. Since the ambient temperatures of the driving transistors inthe pixel units at different positions on the display panel may bedifferent, the threshold voltages of the driving transistors in therespective pixel units may be different. Fluctuation in the thresholdvoltages of the respective driving transistors may cause the displaypanel to display unevenly.

For example, for a display panel using an N-type TFT as a drivingtransistor, if a threshold voltage of the N-type TFT exhibits a negativedrift, the N-type TFT cannot be completely turned off by the OFF statesignal. As a result, the driving current still passes through the drivenOLED and causes the OLED to emit light slightly, thereby causing theblack screen to illuminate and affecting the contrast of the displaypanel.

In order to improve display uniformity of the entire panel, it isnecessary to compensate for the threshold drift of the drivingtransistors in the pixel units. The compensation function can berealized by voltage compensation, current compensation or hybridcompensation. Alternatively, for the pixel circuit, the compensationfunction can be realized by internal compensation, externalcompensation, and the like. For the internal compensation, the pixelcircuit is designed to enable the pixel circuit itself to implement thecompensation function. For the external compensation, an externaldetection circuit is added to the pixel circuit to detect the degree ofthreshold voltage drift of the driving transistor and then modify thedata voltage applied in the display process based on the detectedthreshold voltage drift, thereby eliminating the effect of the thresholdvoltage drift of the drive transistor on the driving current andenabling the display panel to achieve better brightness uniformity. Thecurrent external compensation technology directly detects thresholdvoltage drift of the driving transistor to obtain the compensation valueof the threshold voltage, thereby increasing significantly complexity ofthe pixel circuit on the array substrate and difficulty of wiring.

One embodiment of the present disclosure provides a display panel. Inthe display panel, a second transistor is disposed in a second substrateopposite a first substrate where a driving transistor is located. Thesecond transistor corresponds to the driving transistor. A thresholdvoltage value of the driving transistor may be compensated throughdetection of a threshold voltage of the second transistor. As a result,the complexity of the pixel circuit and the wiring density areeffectively reduced.

FIG. 2 is a block diagram of a display panel provided according to oneembodiment of the present disclosure, and FIG. 3 is a schematic partialcross-sectional view of the display panel of FIG. 2. For the sake ofclarity, only a portion of one pixel unit is shown in FIG. 3. As shownFIG. 2 and FIG. 3, the display panel 10 includes a plurality of pixelunits 100, each of which includes a light emitting element 101 and apixel circuit that drives the light-emitting element 101 to emit light.

In one embodiment, the display panel is an organic light emitting diode(OLED) display panel, and the light-emitting element is an OLED. In oneembodiment, the pixel circuit includes the above 2T1C or an OLED pixelcircuit which has a compensation function, a reset function, and thelike.

In one embodiment, as shown in FIG. 3, the display panel 10 includes afirst substrate 110 and a second substrate 120 disposed opposite eachother. The first substrate 110 and the second substrate 120 areconnected to each other by, for example, an adhesive layer 130. Thefirst substrate 110 includes a first base substrate 111 and a pixel unit100 disposed on the first base substrate 111. In one embodiment, eachpixel unit 100 includes a light emitting element 101 and a firsttransistor 112 that is directly electrically coupled to the lightemitting element 101. The first transistor 112 is a driving transistorin the pixel unit 100, and is configured to operate in a saturated stateand control the magnitude of the current that drives the light-emittingelement 101 to emit light. In another embodiment, a transistor directlycoupled to the light-emitting element 101 may also be a light-emittingcontrol transistor, which is further coupled to the driving transistorfor controlling whether a current for driving the light-emitting element101 to 4 emit light flows. In this embodiment, the driving transistor,which is the first transistor in the embodiment of the presentdisclosure, is an object of compensation. Hereinafter, the firsttransistor 112 will be described as a driving transistor in the pixelunit 100 as an example.

In one embodiment, the display panel 10 may further include a datadriving circuit 23 and a scan driving circuit 24. The data drivingcircuit 23 is configured to emit a data signal as needed (e.g., an imagesignal input to the display apparatus). Each pixel unit of the pixelcircuit may be further configured to receive the data signal and applythe data signal to the gate of the first transistor. The scan drivingcircuit 24 is configured to output various scan signals such as thefirst scan signal SCN1 and the second scan signal SCN2, which will bedescribed below. The scan driving circuit 24 may be a gate drive circuit(GOA) on an integrated circuit chip or directly formed on the displaysubstrate.

In one embodiment, the display panel 10 further includes a controlcircuit 22 configured to perform a driving method according to oneembodiment of the present disclosure to compensate a threshold voltageof a driving transistor of each pixel unit. For example, the controlcircuit 22 may be configured to control the data driving circuit 23 toapply a data signal and control the gate drive circuit 24 to apply ascan signal. In one embodiment, the control circuit 22 is a timingcontrol circuit (T-con).

In one embodiment, the first substrate 110 includes a first basesubstrate 111 and a pixel unit 100 disposed on the first base substrate111. For the sake of clarity, only a portion of one pixel unit is shownFIG. 3. As shown in FIG. 3, each pixel unit 100 includes a lightemitting element 101 and a first transistor 112 for driving thelight-emitting element 101 to emit light. That is, the first transistor112 is a driving transistor in the pixel unit 100. The first transistor112 is disposed between the first base substrate 111 and the lightemitting element 101 and is electrically coupled to the light-emittingelement 101. The light emitting element 101 includes a first electrode1011, a second electrode 1013, and a light emitting layer 1012 disposedbetween the first electrode 1011 and the second electrode 1013. Thefirst transistor 112 includes a gate 1120, a first terminal 1121, asecond terminal 1122, and an active layer 1123. The first electrode 1011of the light-emitting element 101 is electrically coupled to the firstterminal 1121 of the first transistor 112. For example, the firstterminal 1121 is a source or drain of the first transistor 112.

The embodiments of the present disclosure do not limit the type,material, and structure of the light-emitting element 101. For example,the light-emitting element 101 may be a top emission type, a bottomemission type, a double-sided emission type, or the like. Thelight-emitting element 10 may include a hole injection layer, a holetransport layer, an electron injection layer, an electron transportlayer and the like in addition to the light-emitting layer 1012. Thelight-emitting layer may include a polymeric light-emitting material ora small molecule light-emitting material.

The embodiments of the present disclosure do not limit the type,material, and structure of the first transistor 112. For example, thefirst transistor 112 may be a top gate type, a bottom gate type, or thelike, and the active layer may be made of amorphous silicon,polycrystalline silicon (low temperature polycrystalline silicon andhigh temperature polycrystalline silicon), oxide semiconductor or thelike. The first transistor 112 may be an N-type or a P-type.

In one embodiment, the second substrate 120 includes a second basesubstrate 121 and a second transistor 122 disposed on the second basesubstrate 121. The second transistor 122 is disposed corresponding tothe first transistor 112. In one embodiment, the second transistor 122is located in the same pixel region as the first transistor.Furthermore, the second transistor and the first transistor 112substantially overlap or coincide with each other in a directionperpendicular to the panel surface of the display panel (i.e., theorthographic projection of the second transistor 122 on the firstsubstrate 111 and the orthographic projection of the first transistor112 on the first substrate 111 substantially overlap each other). Theterm “substantially” herein means that at least about 90%, preferably atleast about 95%, more preferably at least about 98% of the orthographicprojection of the second transistor on the first substrate overlaps withthe orthographic projection of the first transistor on the firstsubstrate. As such, the second transistor 122 has nearly the samereal-time ambient temperature as the first transistor 112. In oneembodiment, as shown in FIG. 3, the second transistor 122 includes agate 1220, a first terminal 1221, a second terminal 1222, and an activelayer 1223.

The embodiments of the present disclosure do not limit the type,material, and structure of the second transistor 122 except forcorresponding to the first transistor 112. For example, the secondtransistor 122 may be a top gate type, a bottom gate type, or the like.The active layer may be amorphous silicon, polycrystalline silicon (lowtemperature polycrystalline silicon or high temperature polycrystallinesilicon), oxide semiconductor, etc. The second transistor 122 may be aN-type or a P-type.

In one embodiment, the first base substrate 111 and the second basesubstrate 121 are, for example, transparent substrates such as a plasticsubstrate or a glass substrate.

In one embodiment, the threshold voltage characteristic of the firsttransistor 112 corresponds to the threshold voltage characteristic ofthe second transistor 122. That is, the threshold voltage characteristicof the first transistor 112 is proportional to or has a specificrelationship with the threshold voltage characteristic of the secondtransistor 122. As such, the display panel 10 is configured tocompensate the threshold voltage of the first transistor 112 throughdetecting the threshold voltage of the second transistor 122.

In one embodiment, the first transistor 112 has the sametemperature-threshold voltage characteristic as the second transistor122. That is, the temperature has the same effect on the thresholdvoltage of the second transistor 122 and that of the first transistor112. That is, the threshold voltage of the second transistor 122 andthat of the first transistor 112 have the same drifting value and thesame compensation value at a real-time temperature. In this case, thecompensation value of the threshold voltage of the second transistor 122can be measured as the threshold voltage compensation value of the firsttransistor 112. As a result, the threshold voltage of the firsttransistor 112 can be compensated by detecting the threshold voltage ofthe second transistor 122.

In one embodiment, the first transistor 112 is the same as the secondtransistor 122. That is, both the first transistor 112 and the secondtransistor 122 have the same structure and material. In one embodiment,the active layers of the first transistor and the second transistor havethe same size and the same material. In one embodiment, in the casewhere the active layer has a doped region, the doped regions of theactive layers of the first transistor and the second transistor have thesame size and doping concentration. In one embodiment, the channelregions of the active layers of the first transistor and the secondtransistor have the same aspect ratio and the like.

In one embodiment, the first transistor 112 and the second transistor122 are both thin film transistors.

In one embodiment, both the first transistor 112 and the secondtransistor 122 are either a top gate structure or a bottom gatestructure.

In one embodiment, both the active layer 1123 of the first transistor112 and the active layer 1223 of the second transistor 122 include ametal oxide semiconductor material, such as indium gallium zinc oxide(IGZO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), or zincoxide (ZnO), etc. In one embodiment, the composition ratio of threeelements, indium, gallium, and zinc in indium gallium zinc oxide is1:1:4.

In one embodiment, the first transistor 112 has a similartemperature-threshold voltage characteristic curve as the secondtransistor 122. For example, the first drift value of the thresholdvoltage of the first transistor 112 caused by the temperature isproportional to or in a certain relationship with the second drift valueof the threshold voltage of the second transistor 122 caused by thetemperature. In this case, the drift value and the compensation value ofthe first threshold voltage of the first transistor 112 can be inferredbased on the measured drift value and the compensation value of thesecond threshold voltage of the second transistor 122. As such, thefirst threshold voltage of the first transistor 112 can be compensatedby detecting the second threshold value of the second transistor 122.

In one embodiment, the second substrate 120 includes a plurality ofsecond transistors 122, and the plurality of second transistors 122 arein one-to-one correspondence with the plurality of first transistors 112of the plurality of pixel units 100 in the first substrate. As such, thefirst transistors 112 may have closer positional relationship with thecorresponding second transistors 122 respectively, thereby being in amore real-time temperature environment. In this case, the thresholdvoltages of the second transistors 122 are detected in order tocompensate the threshold voltages of the corresponding first transistors112 respectively.

In one embodiment, the second substrate 120 is divided into a pluralityof regions, each of which corresponds to a plurality of pixel units 100.Each region is provided with a second transistor 122. The secondtransistor corresponds to the plurality of pixel units 100 correspondingto the region. That is, the second transistor 122 also corresponds tothe plurality of first transistors 112 of the plurality of pixel units100 in the corresponding region. As such, the distribution density ofthe second transistors 122 can be reduced. In one embodiment, the secondsubstrate 120 may be divided into a plurality of regions according topixels, and one pixel includes, for example, three or more pixel units100 to cooperate to emit light of a certain color. The plurality ofpixel units in one pixel is relatively close in terms of not only thepositional relationship, but also the luminescence time. As such, thefirst transistors 112 of the plurality of pixel units 100 in one pixelare in a nearly same real-time temperature environment. In this case, asecond transistor may be disposed corresponding to the plurality ofpixel units 100 in one pixel. That is, one second transistor correspondsto a plurality of first transistors 112 in a plurality of pixel units100.

In one embodiment, one pixel includes three pixel units 100 (forexample, RGB). One second transistor 122 may be disposed correspondingto three pixel units 100 in one pixel. That is, one second transistor122 corresponds to three first transistors 112. In one embodiment, onepixel includes four pixel units 100 (for example, RGBW). One secondtransistor 122 may be disposed corresponding to four pixel units 100 inone pixel. That is, one second transistor 122 corresponds to four firsttransistors 112. In this case, by detecting the threshold voltage of thesecond transistor 122, the threshold voltages of the plurality ofcorresponding first transistors 112 can be compensated.

In one embodiment, the second substrate 120 further includes a detectioncircuit 11 electrically coupled to the second transistor 122 to detectthe threshold voltage of the second transistor 122 in real time.

FIG. 4 shows a structure of a detection circuit according to oneembodiment of the present disclosure. As shown in FIG. 4, the detectioncircuit 11 includes a third transistor T3, a fourth transistor T4, afirst capacitor C1, and a detection line 140. The gate and the firstterminal of the third transistor T3 are configured to respectivelyreceive the first scan signal SCN1 and the data signal DATA, and thesecond terminal of the third transistor T3 is coupled to the gate of thesecond transistor 122. The first and second terminals of the secondtransistor 122 are respectively coupled to the first power voltage Vddand the first terminal of the fourth transistor T4. The gate of thefourth transistor T4 is configured to receive the second scan signalSCN2, and the second terminal of the fourth transistor is coupled to thedetection line 140 for receiving the detection signal SENSE. The firstcapacitor C1 is coupled between the gate and the second terminal of thesecond transistor 122. The first scan signal SCN1, the second scansignal SCN2, and the data signal DATA are provided by the correspondinggate lines and data lines disposed on the second substrate. Thecorresponding gate lines and data lines disposed on the second substrateare, for example, electrically coupled to the separately provided gatedriving circuit and data driving circuit. The gate driving circuit andthe data driving circuit may be disposed on the second substrate.Alternatively, the gate driving circuit and the data driving circuit maybe disposed on the first substrate and are coupled to the gate lines andthe data lines on the second substrate through a conductive path (forexample, an anisotropic conductive paste) disposed between the firstsubstrate and the second substrates. For example, the data signal DATAsupplied to the detecting circuit may be a specific reference datasignal for detection such as a stable voltage signal. As such, a datadriving circuit may not be needed, and a voltage terminal or a circuitthat outputs the stable voltage signal may be used instead.

In one embodiment, the detection line 140 is coupled to a samplingcircuit 150 to sample electrical signals on the detection line 140. Thesampling circuit may be, for example, a conventional sampling circuitincluding an amplifier and an analog-to-digital converter (ADC), etc.,which is not described in detail in the embodiments of the presentdisclosure.

In the following, the detection method of the detection circuit isexemplified by taking the second transistor 122, the third transistorT3, and the fourth transistor T4 as N-type transistors for an example.However, the embodiment of the present disclosure does not limit this.

In one embodiment, the detection method includes: at a first moment,both the first scan signal SCN1 and the second scan signal SCN2 providean on signal and a data signal DATA and a detection signal SENSE arealso provided. In this case, the third transistor T3 and the fourthtransistor T4 are both turned on. As such, the data signal DATA istransmitted to the gate of the second transistor 122 and the firstelectrode of the first capacitor C1 via the third transistor T3. Thedetection signal SENSE passes through the fourth transistor T4 and istransmitted to the second terminal of the second transistor 122 and thesecond electrode of the first capacitor C1. Under the action of thefirst power voltage Vdd, a driving current is generated in the secondtransistor 122 and charges the second electrode of the first capacitorC1 to Vdata-Vth, wherein Vth is the threshold voltage of the secondtransistor 122. At this time, the second transistor 122 is turned fromthe on state to the off state. At the second moment, the first scansignal SCN1 and the second scan signal SCN2 both provide an on signal,and the third transistor T3 and the fourth transistor T4 are both turnedon. The second electrode of the capacitor C1 is sampled by the samplingcircuit 150 to obtain the threshold voltage Vth of the second transistor122.

In one embodiment, as shown in FIG. 3, the second substrate 120 furtherincludes a light shielding layer 123. The second transistor 122 islocated in a region where the light shielding layer 122 is located orcovered, so that the second transistor 122 is protected by the lightshielding layer 123 from ambient light outside the display panel,thereby avoiding the adverse effects of the ambient light on thedetection result. In one embodiment, the orthographic projection of thesecond transistor 122 on the second base substrate 121 falls within theorthographic projection of the light-shielding layer 123 on the secondbase substrate 121. In one embodiment, the light-shielding layer 123 ismade of an opaque metal material such as copper, aluminum, or magnesium,or a metal alloy material, or a black resin.

In one embodiment, the light-emitting element 101 is a double-sidedlight-emitting structure, and the first electrode 1011 and the secondelectrode 1013 of the light-emitting element 101 are made of both lighttransmissive or semi-transmissive materials. As such, the display panel10 forms a double-sided display structure. In one embodiment, the firstelectrode 1011 is made of a transparent metal oxide conductive materialhaving a high work function, such as indium tin oxide (ITO) or the like.The second electrode 1023 has, for example, a laminated structure of ametal material and a transparent metal oxide material such as an Ag/ITOlaminate structure.

In one embodiment, as shown in FIG. 3, the light emitting element 101 isa double-sided light emitting structure. The first substrate 110 and thesecond substrate 120 respectively include a first color filter layer 114and a second color filter layer 124. The first color filter layer 114 isdisposed between the first transistor 112 and the light emitting element101, and the second color filter layer 124 is disposed between thesecond transistor 122 and the light-emitting element 101. The orthogonalprojection of the first color filter layer 114 and that of the secondcolor filter layer on the first base substrate 111 respectivelysubstantially overlap with the orthographic projection of thelight-emitting element 101 on the first base substrate 111.

In one embodiment, in the second substrate 120, between the filter unitsof different colors of the second color filter layer 124, a black matrixstructure is further provided for preventing light leakage and colorseparation. The first substrate 110 can also be similarly arranged, anddetails are not described herein again. The black matrix can be preparedfrom a metal oxide or a black resin by a photolithography process, orthe like.

In one embodiment, the light-emitting element 101 may also be a toplight-emitting structure or a bottom light-emitting structure. In thiscase, a filter layer may be respectively disposed in the secondsubstrate 120 or the first substrate 110, and the details thereof arenot described herein again.

In one embodiment, the control circuit 22 is further configured toperform the above-described detection method to detect the thresholdvoltage of the second transistor 122 of each pixel unit in real time.For example, the control circuit 22 is configured to control thedetection circuit 11 to detect the threshold voltage of the secondtransistor 122 in real time.

Another example of the present disclosure further provides a drivingmethod of the display panel 10 described above. The driving method mayinclude: compensating a threshold voltage of the first transistor 121 bydetecting a threshold voltage of the second transistor 122. As describedabove, the above-described driving method is made possible because thethreshold voltage characteristic of the first transistor 112 correspondsto the threshold voltage characteristic of the second transistor 122.That is, the threshold voltage characteristic of the first transistor112 is proportional to or has a specific relationship with the thresholdvoltage characteristic of the second transistor 122.

In one embodiment, the drift value (compensation value) of the firstthreshold voltage of the first transistor 112 caused by a certaintemperature is proportional to or has a specific relationship with thedrift value (compensation value) of the second threshold voltage of thesecond transistor 122 caused by the certain temperature. The drivingmethod includes: establishing a correspondence relationship between athreshold voltage compensation value of the second transistor 122 and athreshold voltage compensation value of the first transistor 112, andusing the correspondence relationship and the detected threshold voltageof the second transistor to compensate the threshold voltage of thefirst transistor 112. In one embodiment, the compensation value of thethreshold voltage of the second transistor can be obtained by detectingthe real-time threshold voltage value of the second transistor 122 and astandard value of the threshold voltage of the second transistor 122(for example, a standard threshold voltage value under room temperaturecondition). Because the ambient temperature of the first transistor 112and that of the second transistor 122 are nearly the same, the thresholdvoltage compensation value of the first transistor 112 can be inferredbased on the correspondence relationship between the threshold voltagecompensation value of the second transistor 122 and the thresholdvoltage compensation value of the first transistor 112. Then, thethreshold value of first transistor 112 is compensated based on thethreshold voltage compensation value of the first transistor 112.

In one embodiment, the driving method further includes performingthreshold compensation of the first transistor 112 by an externalcompensation circuit. The resulting threshold voltage compensation valueof the first transistor 112 may be stored in the control circuit 22 in alookup table.

In one embodiment, the first transistor 112 and the second transistor122 have the same temperature-threshold voltage characteristic curve. Inthis case, since the ambient temperatures of the first transistor 112and the second transistor 122 are nearly the same, the threshold voltagecompensation value of the second transistor 122 can be regarded as thethreshold voltage compensation value of the first transistor 111.

In one embodiment, the driving method includes acquiring a real-timetemperature by detecting a threshold voltage of the second transistor122, and compensating for a threshold voltage of the first transistor112 based on the real-time temperature.

In one embodiment, the driving method includes: acquiring atemperature-threshold voltage relationship curve of the secondtransistor 122; obtaining a real-time temperature by detecting athreshold voltage of the second transistor 122 in connection with thetemperature-threshold voltage relationship curve of the secondtransistor 122; obtaining a temperature-threshold voltage relationshipcurve of the first transistor 112; and obtaining the threshold voltagecompensation value of the first transistor 112 by using thetemperature-threshold voltage relationship curve of the first transistor112 and the real-time temperature.

In one embodiment, the temperature-threshold voltage characteristiccurves of the first transistor 112 and the second transistor 122 may berespectively measured before the first substrate 110 and the secondsubstrate 120 are bonded to each other.

FIG. 5 shows an example of a temperature-threshold voltagecharacteristic curve of the second transistor 122 according to oneembodiment of the present disclosure. As shown in FIG. 5, thetemperature-threshold voltage characteristic curve of the secondtransistor 122 is obtained by detecting the threshold voltages of thesecond transistor 122 at four different temperatures, that is, 20° C.,40° C., 60° C., and 80° C.

In one embodiment, since the threshold voltage has a one-to-onecorrespondence with the temperature, after the detection circuit 11detects the real-time threshold voltage of the second transistor 122,the real-time temperature T of the second transistor 122 is obtained byconsulting with the temperature-threshold voltage characteristic curve.Then, using the real-time temperature T in consultation with thetemperature-threshold voltage characteristic curve of the firsttransistor 112, a real-time threshold voltage of the first transistor112 is determined. Then, the threshold voltage compensation value isobtained by comparing the real-time threshold voltage of the firsttransistor 112 with the standard value of the threshold voltage of thefirst transistor 112 (such as a threshold voltage value at a roomtemperature).

In one embodiment, the control circuit 22 is also configured to performthe driving method provided by embodiments of the present disclosure tocompensate for the threshold voltage of first transistor 112 of eachpixel unit. For example, the control circuit 22 is configured to controlthe external compensation circuit to compensate for the thresholdvoltage of first transistor 112.

In one embodiment, the control circuit 22 can be in various forms. Inone embodiment, the control circuit includes a processor 221 and amemory 222. The memory 222 includes executable code and the processor221 can run the executable code to perform the detection methoddescribed above.

In one embodiment, the processor 221 can be a central processing unit(CPU) or other form of processing device having data processingcapabilities and/or instruction execution capabilities such as amicroprocessor, programmable logic controller (PLC), or the like.

In one embodiment, the memory 222 can include one or more computerprogram products, which can include various forms of computer readablestorage media such as volatile memory and/or nonvolatile memory.Volatile memory can include, for example, random access memory (RAM)and/or caches and the like. The non-volatile memory may include, forexample, a read only memory (ROM), a hard disk, a flash memory, or thelike. One or more computer program instructions can be stored on acomputer readable storage medium, and processor 221 can execute thefunctions desired by the program instructions. Various applications andvarious data such as threshold voltage compensation value data acquiredin the above-described detection method, and the like can also be storedin the computer readable storage medium.

Another example of the present disclosure provides a method of formingthe display panel according to one embodiment of present disclosure. Thelaminated structure of the display panel prepared in this embodiment mayinclude a transparent substrate layer, a light shielding layer, a bufferlayer, a semiconductor layer, a gate insulating layer, an intermediatedielectric layer, a source and drain layer, and a passivation layer. Inone embodiment, the method may include forming a second substrate havinga structure as shown in FIG. 6A and forming a first substrate having astructure as shown in FIG. 6B separately. As shown in FIG. 6A, thesecond substrate may include a glass substrate 1 as a transparent basesubstrate, a light shielding layer 2, a buffer layer 3, a semiconductorlayer 4, a gate insulating layer 6, an intermediate dielectric layer 7,a source and drain layer 8, a passivation layer 9, a color filter 10, ablack matric 11, and OC 12. As shown in FIG. 6B, the first substrate mayinclude a glass layer 12, a buffer layer 13, a semiconductor layer 14, agate insulating layer 16, an intermediate dielectric layer 17, a sourceand drain layer 18, a passivation layer 19, a color filter 20, a resinlayer 21, an anode 22, and a pixel defining layer 23.

Then, the first substrate and the second substrate are aligned andcombined to form the display panel having a structure as shown in FIG.6C. As shown in FIG. 6C, an emission layer 24, a cathode layer 25, and afiller layer 26 are also formed between the first substrate and thesecond substrate.

Some embodiments of the present disclosure provide a display panel, amanufacturing method thereof, and a driving method thereof. By setting asecond transistor corresponding to a driving transistor in a pixel unit,and compensating for a threshold voltage of the driving transistor bydetecting a threshold voltage of the second transistor, the complexityof the pixel circuit and the wiring density can be effectively reduced.

The principle and the embodiment of the present disclosures are setforth in the specification. The description of the embodiments of thepresent disclosure is only used to help understand the method of thepresent disclosure and the core idea thereof. Meanwhile, for a person ofordinary skill in the art, the disclosure relates to the scope of thedisclosure, and the technical scheme is not limited to the specificcombination of the technical features, and also should covered othertechnical schemes which are formed by combining the technical featuresor the equivalent features of the technical features without departingfrom the inventive concept. For example, technical scheme may beobtained by replacing the features described above as disclosed in thisdisclosure (but not limited to) with similar features.

1. A display panel, comprising: a. first substrate, the first substratecomprising a pixel it, the pixel unit comprising a light emittingelement and a first transistor for driving the light emitting element toemit light; a second substrate opposite the first substrate, the secondsubstrate comprising a second transistor, wherein the second transistoris configured to have a second drift value of a second threshold voltagewhich has a specific relationship with a first drift value of a firstthreshold voltage of the first transistor under same ambient condition.2. The display panel according to claim 1, wherein the first drift valueof the first threshold voltage of the first transistor caused by atemperature is substantially the same as the second drift value of thesecond threshold voltage of the second transistor caused by thetemperature.
 3. The display panel according to claim 1, wherein thesecond transistor is substantially identical in structure and materialas the first transistor, and the specific relationship is that thesecond drift, value is proportional to the first drift, value.
 4. Thedisplay panel according to claim 1, wherein active layers of the firsttransistor and the second transistor have the same size and are made ofthe same material, and the specific relationship is that the seconddrift value is the same as the first drift value.
 5. The display panelaccording to claim 4, wherein doped regions of the active layers of thefirst transistor and the second transistor have the same size and dopingconcentration.
 6. The display panel according to claim 4, whereinchannel regions of the active layers of the first transistor and thesecond transistor have the same aspect ratio.
 7. The display panelaccording to claim 1, wherein an orthographic projection of the secondtransistor on the first substrate substantially overlaps an orthographicprojection of the first transistor on the first substrate.
 8. Thedisplay panel according to claim 1, wherein the pixel unit comprises aplurality of pixel units, the plurality of pixel units comprising aplurality of first transistors, the second substrate comprises aplurality of second transistors, and the plurality of second transistorsare in one-to-one correspondence with the plurality of firsttransistors.
 9. The display panel according to claim 1, wherein thepixel unit comprises a plurality of pixel units, the plurality of pixelunits comprising a plurality of first transistors, the second substratecomprises a plurality of second transistors, and each of the pluralityof second transistors corresponds to two or more of the plurality offirst transistors.
 10. The display panel according to claim 1, whereinthe second substrate further comprises a detection circuit coupled tothe second transistor, and the detection circuit is configured to detectthe second threshold voltage of the second transistor.
 11. The displaypanel according to claim 10, wherein the detecting circuit comprises athird transistor, a fourth transistor, and a first capacitor; a gate anda first terminal of the third transistor are configured to respectivelyreceive a first scan signal and a data signal, and a second terminal ofthe third transistor is coupled to a gate of the second transistor; afirst terminal and a second terminal of the second transistor arerespectively coupled to a first power voltage and a first terminal ofthe fourth transistor; a gate and a second terminal of the fourthtransistor are respectively configured to receive a second scan signaland a detection signal respectively; and the first capacitor is coupledbetween the gate and the second terminal of the second transistor. 12.The display panel according to claim 1, wherein the second substratefurther comprises a light shielding layer, and the light shielding layeris configured to shield the second transistor from external ambientlight.
 13. The display panel according to claim 1, wherein the firstsubstrate and the second substrate respectively comprise a first colorfilter layer and a second color filter layer; the first color filterlayer is in an area between first black matrix covering the firsttransistor; and the second color filter layer is in an area betweensecond black matrix covering the second transistor.
 14. The displaypanel according to claim 13, wherein an orthogonal projection of thefirst color filter layer and that of the second color filter layer on afirst base substrate respectively substantially overlap with anorthographic projection of the light-emitting element on the first basesubstrate.
 15. The display panel according to claim 1, wherein thedisplay panel is an organic light emitting diode display panel.
 16. Amethod of driving the display panel according to claim 1, comprising:compensating for the first threshold voltage of the first transistor bydetecting the second threshold voltage of the second transistor.
 17. Thedriving method according to claim 16, further comprising: establishing aspecific relationship between a threshold voltage compensation value ofthe second transistor and a threshold voltage compensation value of thefirst transistor, and compensating for the threshold voltage of thefirst transistor by detecting the threshold voltage of the secondtransistor comprises: compensating for the threshold voltage of thefirst transistor by using the specific relationship and the detectedthreshold voltage of the second transistor.
 18. The driving methodaccording to claim 17, wherein the threshold voltage compensation valueof the second transistor is substantially equal to the threshold voltagecompensation value of the first transistor.
 19. The driving methodaccording to claim 16, further comprising: obtaining a real-timetemperature by detecting the threshold voltage of the second transistor,and compensating for the threshold voltage of the first transistor bydetecting the threshold voltage of the second transistor comprises:compensating for the threshold voltage of the first transistor based onthe real-time temperature.
 20. The driving method of claim 19, whereinobtaining the real-time temperature by detecting the threshold voltageof the second transistor comprises: obtaining a temperature-thresholdvoltage relationship curve of the second transistor, acquiring thereal-time temperature by detecting the threshold voltage of the secondtransistor and consulting with the temperature-threshold voltagerelationship curve of the second transistor; and compensating for thethreshold voltage of the first transistor based on the real-timetemperature comprises: obtaining a temperature-threshold voltagerelationship curve of the first transistor, and acquiring the thresholdvoltage compensation value of the first transistor by using thereal-time temperature and consulting with the temperature-thresholdvoltage relationship curve of the first transistor.